unforeseen       
adjective uk/ˌʌn.fəˈsiːn/ us/ˌʌn.fɚˈsiːn/
C1 未预见到的;意料之外的
not expected
  Due to unforeseen circumstances the cost of the improvements has risen by 20 percent. 由于出现了意外情况,装修成本增加了20%。 
 Unless there are any unforeseen problems the whole project should be finished by the spring. 除非出现什么意外情况,整个工程应该在春季前完工。 
 Synonyms: unexpectedunlooked-for